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    Droplets in a deodorant spray have a mass of about 4*10^-12 kg
    and a radius of 0.1mm
    estimate the the terminal velocity in air of viscosity 2*10^-5
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    Direct yourself to the 'Maths, Science, and Technology Help' sub-forum in future when asking these sorts of questions. Anyway, I haven't done much about terminal velocity but maybe this website would help you? http://www.sciencebyjones.com/viscosity.htm

    You just need to find the speed at which the force of gravity equals the forces acting upwards . . .
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    (Original post by reb0xx)
    Droplets in a deodorant spray have a mass of about 4*10^-12 kg
    and a radius of 0.1mm
    estimate the the terminal velocity in air of viscosity 2*10^-5
    There is one force acting downwards, the weight of the particle. That's just mg.

    There are two forces acting upwards

    *the viscous drag force F
    *the buoyancy (Archimedes upthrust) force U

    At terminal velocity mg = F + U

    The F term for viscous drag includes the velocity which you are trying to calculate.

    Do you have formulas for F and U?

    Note: some questions will direct you to ignore the U term.
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    (Original post by Stonebridge)
    There is one force acting downwards, the weight of the particle. That's just mg.

    There are two forces acting upwards

    *the viscous drag force F
    *the buoyancy (Archimedes upthrust) force U

    At terminal velocity mg = F + U

    The F term for viscous drag includes the velocity which you are trying to calculate.

    Do you have formulas for F and U?
    F=6pirnv always.
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    (Original post by Mr Edexcel)
    F=6pirnv always.
    Put that equal to mg and calculate v.
    You have m, r and n (viscosity) all given. Assume values for g and Pi.
    If you are supposed to include the U term you need to know the density of air. Is it given?
 
 
 
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